1. Field of the Invention
The present invention relates to a rotating cup coating device which is used to rotate a material to be treated after a coating liquid has been dropped onto the surface thereof for forming a coat of the liquid on the surface of the material to be treated such as a glass substrate or a semiconductor wafer or the like. Such coating device shall be referred to as a "rotating cup type liquid coating device" hereinbelow.
2. Description of the Relevant Art
There is already known a rotating cup type liquid coating device comprising an inner cup which is driven to rotate by a spinner, an outer cup disposed outside of the inner cup, and lid bodies, each of which selectively closes an open upper surface of the respective cup, as disclosed in Japanese Laid-Open Patent Publication No. 7-132263 (1995).
According to the known device, a penetrating hole is formed on the lid body for the inner cup and a valve is provided in a portion of the penetrating hole. Further, penetrating holes are also formed on lifting bodies for lifting up the lid bodies for the inner and outer cups. The function thereof is for preventing the dust floating around outside the cups from flowing into the inside of the cups when the lid bodies are opened, by decreasing the pressure difference between the inside of the inner cup and to the outside in advance of opening the lid bodies after the completion of a rotating and coating operation by the device. Particularly, the pressure is decreased through introducing gas (air) into the depressurized closed space defined between the inner cup and the lid body of the inner cup via the penetrating holes by opening the valve.
With the construction mentioned above, although it is possible to eliminate the disadvantage caused by the depressurization of the space defined between the inner cup and the lid body during the rotating and coating of the device, the device is undesirably more complicated in its construction because of forming of a special shape of the penetrating hole and a necessity of further provision of the valve.